A bony toothed bird from the Purisima Formation, part 2

After I got the bone identified as a bird, I emailed pictures to my colleague N. Adam Smith, who at the time was a Ph.D. student at University of Texas at Austin, studying with Julia Clarke. We both agreed on the identification of the specimen as a pelagornithid, and also agreed that it could be written up quickly, and we immediately began working on the manuscript. This was the fastest paper I ever wrote - partially because each of us did about 50% of the work, and we went through a bazillion drafts (a new draft every 24-36 hours for four weeks in September and October), and we finally submitted it on Halloween.


We were pretty anal about properly figuring and labeling all the anatomic structures of this specimen in our paper; we were wholly dissatisfied with previous papers which had not labeled the relatively divergent anatomical structures of pelagornithid humeri sufficiently. Many anatomical features are fairly modified relative to non-pelagornithids, and without adequately labeled (or unlabeled) figures, it is difficult for the non-specialist to interpret their morphology; we thought we'd do everyone a favor and do it properly. One exception is Bourdon et al. (2010), who studied Eocene pelagornithids from Morocco (whose paper was also not out yet when we submitted our article).

Figure 2 from our paper, highlighting the anatomical structures of UCMP 219007.

A comparison of humeri of pelagornithids and modern pelecaniform and procellariiform birds. A- Pelagornis sp. (UCMP 219007); B- Pelagornis chilensis, late Miocene, Bahia Inglesa, Chile (holotype, from Mayr and Rubilar-Rogers 2010); C- Pelagornis miocaena, Miocene, France; D- Pelagornis sp., Pisco Formation, Peru (Pliocene); E- Morus bassanus, Gannet, extant (CAS specimen); F- Phoebastria irrorata, Waved Albatross, extant (CAS specimen); G - cf. Macrodontopteryx (synonymized with Dasornis iby Bourdon, 2010), Eocene, Belgium; H- Pelagornis mauretanicus, Pliocene, Morocco.

Many features of pelagornithids (and specifically, Pelagornis spp.) are highly divergent relative to other pelecaniformes (as you can see above, compared with Morus). Additionally, as you can see, our specimen is one of the most well preserved pelagornithid humeri now known, even more so than the beautiful holotype of Pelagornis chilensis, the humerus of which still has quite a bit of matrix encrusted and glued onto the bone, obscuring some of the fossae. One of the pneumatic fossae is actually pneumatized, and bears a pneumatic foramen that appears to connect to the internal cavity of the bone, a condition we had not read about or observed in any fossil or modern relative.

Shaded drawing I made and used for figure 3 of our paper, showing the pneumatic foramen.

Lastly, for our paper I thought I would try a skeletal reconstruction of Pelagornis. It was on my to-do list for the paper, and we already had a couple of drafts sent back and forth when Pelagornis chilensis graced the cover of JVP: it couldn't have been more timely. Although not in the original paper, associated with the press release were several skeletal reconstructions. I emailed the artist Carlos Anzures in Chile to ask for permission to modify it for our study. Well, I didn't just modify it; I redrew it by hand, reposed it, inked the drawing on vellum, and then edited the image in adobe illustrator, to eventually get something like what you see below:

Part of Figure 1 of our paper, showing the skeletal reconstruction of Pelagornis.

Next time: more on pelagornithid evolution and ecology, as well as biogeography and the implications of our find.

Bourdon, E., Amaghzaz, M., and Bouya, Baadi. 2010. Pseudotoothed birds (Aves, Odontopterygiformes) from the Early Tertiary of Morocco. American Museum Novitates 3704:1-71.

Mayr, G., and D. Rubilar-Rogers. 2010. Osteology of a new giant bonytoothed bird from the Miocene of Chile, with a revision of the taxonomy of Neogene Pelagornithidae. Journal of Vertebrate Paleontology 30:1313–1330.

A bony toothed bird from the Purisima Formation, part 1

One foggy morning while doing fieldwork in the Purisima Formation, I spotted a cylindrical bone in the base of a cliff. It initially appeared hollow, but at the time of discovery, I wasn't so sure - sometimes mud and weathering products can obscure certain details of an exposed fossil. Eventually, I decided that it was most likely hollow - I scratched the inside of the bone, and had grains of ancient sand in my palm rather than bone fragments. The first step of excavating a fossil is trying to identify it: if you are positive about A) what bone you have discovered, B) what taxon it belongs to, and C) how it is oriented, you may excavate the fossil in a large block and not damage it. Sometimes you cannot limit your identification to one taxon, and this case was an example.

The end of the bone as it was exposed in the field.

Given the size of the bone, and how common marine mammals are, I assumed the most likely possibility was some sort of a fossil odontocete (toothed whale) jaw: the posterior lower jaws of odontocetes are hollow, and walled with thin bone. The only problem with this identification was that in cross section, odontocete jaws are flattened and sometimes nearly kidney-shaped - while this specimen had a more oval cross section. Nevertheless, it was my best guess at the time. When confronted by a situation like this- where you are uncertain of points A and B above, the best option is to carefully expose as much as possible until you can positively identify it. This is sometimes called "field prepping" (i.e. preparation), and sometimes may result in fragile bits of bones being broken off if you screw up or make a mistake while excavating (because field tools are less precise than lab tools, among other reasons). Aside from potentially resulting in breakage, field prepping takes time - time you may not have, if for example, you are working at low tide within the intertidal zone and have two hours left to finish.

The two sides of the unidentified bone.

Towards the end of the excavation, it was becoming clear that whatever I had found was something strange. I still thought I had an odontocete jaw, and at the time it was my best guess (I'll explain why later). I joked to myself in the field "Perhaps you've found the world's first Pliocene pterosaur!" Little did I know, I was more right about that joke than I realized at the time.

It had a slight curve to it, but it did not fan out at the posterior end like it should have if it were a jaw. I collected it in three big pieces, and upon these coming out, I saw that the sediment inside the bone was cemented - explaining why it was so well preserved, and not crushed. When I began preparing it at home, I was surprised to see that there was no enlarged mandibular foramen - again, a large hole should have been there - but instead, there was no opening in the bone.

A dentary of the bottlenose dolphin Tursiops; the enlarged posterior end and mandibular foramen can be seen on the right side of the picture (from Mead and Fordyce, 2009).

So what the hell was it? Upon leaving the field, I thought all I had was some weird odontocete with a strangely shaped jaw - perhaps a small sperm whale; they often have skinny lower jaws. However, I was once again surprised (and frustrated) by my lack of an identification, now that I had prepared the end of it (whichever end it was!). So I took a guess: some sort of a large bird bone. I did not take my thought too seriously, but the bone was in fact hollow, so I humored myself and opened up my copy of Lee Creek Volume III, and flipped to the article on the Yorktown Fm. bird assemblage.

One side of the complete end of the mystery bone.

The other end of the mystery bone.

Lo and behold, I had a match! The proximal end was a nearly exact match with the proximal fragment of a Pelagornis humerus figured by Olson and Rasmussen (2001); Pelagornis is a gigantic extinct species of bony toothed bird. I couldn't believe it: there was a very specific reason that I had not considered a bird as the owner of the unidentified bone: it was too large to represent any bird already known from the Purisima Formation, even a pelican or an albatross (in fact, it was over twice the size). I did not consider a pelagornithid simply because there are no documented occurrences of pelagornithids in younger than early Late Miocene rocks from the eastern North Pacific: there are plenty of Middle Miocene records of the bird Osteodontornis,

and a couple of records of it from the Monterey Formation. I had always assumed that they had gone extinct in the NE Pacific before the Pliocene; not only that, but this was a late Pliocene fossil. There are some Tortonian stage-like critters from the lowermost Purisima - a possible record of Imagotaria, as well as Megaptera miocaena, a Nannocetus-like cetotheriid, a possible record of Dusisiren, and some odds and ends - but this bird was far, far younger than this assemblage.Comparison of the fossil pelagornithid humerus (A, C) with the fragment from the Pliocene Yorktown Formation of North Carolina figured by Olson and Rasmussen (2001).

Check back for part 2, soon.

References:

Boessenecker, R.W. and N.A. Smith. 2011. Latest Pacific basin record of a bony-toothed bird (Aves, Pelagornithidae) from the Pliocene Purisima Formation of California, U.S.A. Journal of Vertebrate Paleontology 31(3):652-657.

Mead, J. G., and R. E. Fordyce. 2009. The therian skull: a lexicon with emphasis on the odontocetes. Smithsonian Contributions to Zoology 627:1-248.

Olson, S. L., and P. C. Rasmussen. 2001. Miocene and Pliocene birds from
the Lee Creek Mine, North Carolina. Smithsonian Contributions to
Paleobiology 90:233–365.

Sixth Triennial conference on the Secondary Adaptation of Tetrapods to Life in the Water

Two weeks ago today, I delivered a presentation on the first day of the 2011 Aquatic Tetrapods conference in beautiful San Diego, California. I had eight hours on my drive down to San Diego the day before to worry about how screwed I was: the last time I gave that presentation, it was only 20 slides longer, and took 50 minutes to deliver. I practiced it once Monday morning in front of Joe El Adli (our gracious host), and Yale students Rachel Racicot and Daniel Field - I barely fit it into 20 minutes. It all worked out fine, and in the actual presentation, I finished the last conclusion slide right as it counted down to zero. This was a fresh break from SVP tradition, which dicates that cetacean research is presented on the afternoon of the last day, giving you all week to worry about the presentation. This time, I was able to relax during the entire meeting.

My title slide for my taphonomy presentation.

It would be very difficult to summarize all the research presented, but I might be able to summarize a few of the highlights that stick out in my mind. Julia Fahlke (University of Michigan) gave a fascinating talk Monday Morning about basilosaurid and protocetid cetaceans with asymmetrical crania, and implications for the evolution of hearing underwater. I'll admit, when I read the abstract I was skeptical, but her presentation was pretty compelling - I'll wait to say more until it gets published, though. Brian Beatty presented some details of his research on meningeal ossification in cetacea, which appears to not be homologous to that in many other mammals. Larry Barnes showed us a new Paleoparadoxia skeleton the LACM has been working on from the Monterey Formation; it's virtually complete, with a very large, gnarly looking skull. Olivier Lambert gave a talk coauthored by Giovanni Bianucci on a new large assemblage of bizarre ziphiid fossils dredged from the seafloor off the coast of Spain; boy, there are some real freaks. Our Australian colleague Erich Fitzgerald presented a new juvenile aetiocetid skull from the Oligocene of Washington State which he's been slowly preparing with acid; needless to say, it's a beautiful specimen. Manuel Martinez, a Peruvian who is Christian de Muizon's Ph.D. student, presented on an incredible new toothed mysticete from the Oligocene of Peru - I won't give any details, but lets just say this will be a very, very important specimen.

Frank Fish gives a mini presentation on locomotor adaptations of various marine mammals, using an assortment of articulated limbs (a walrus forelimb is seen in the foreground).

On wednesday, we went over to the San Diego Natural History Museum for an osteology workshop on aquatic tetrapods. Due to the research focus of Tom Demere (Paleo curator) and Annalisa Berta, the majority of material out on display was from modern and fossil marine mammals. There was a great assortment of wonderful stuff out, and it was amazing to be there with so many other marine mammal (and otherwise) researchers there.

Several cetacean researchers are in this photo: Toshiyuki Kimura (foreground), Mette Steeman (behind "Tosh"), and Giovanni Bianucci (background, left) and Joe El Adli (background, right).

At the workshop, I caught Brian Beatty red-handed demonstrating his very technical method to determine the relative height of the bony tentorium (here on a skull of the Amazon river dolphin, Inia geoffrensis).

For a while, Daryl Domning gave a short presentation on the locomotion and forelimb of sirenians (using a Manatee forelimb skeleton).

Here, some of the brightest minds in cetacean paleontology scrutinize one of the weirdest fossil mysticetes: a new species of Herpetocetus under study by Joe El Adli. From left to right: Mette Steeman, Joe El Adli (standing), Felix Marx (leaning over skull), Meredith Rivin (background), Giovanni Bianucci (in glasses), and Olivier Lambert (in red).

Manuel Martinez, a Peruvian researcher studying with Christian de Muizon in Paris, did not waste a chance to photobomb. Here he is photographed with a cast of the skull of the bizarre extinct edentulous* walrus Valenictus chulavistensis.

Daryl Domning again gives a short presentation, this time on sirenian crania. Here he is showing a cast of the skull of the world's largest sirenian, the extinct Pliocene species Hydrodamalis cuestae (the ancestor of the "modern" Steller's Sea Cow).

My (soon to be) coauthor Morgan Churchill photographs an articulated hindlimb of the modern walrus.

Rachel Racicot (and Daniel Field) hung out with me for a bit in the type room at the San Diego Natural History museum while I photographed some fossil pinniped material. Skulls of gigantic Hydrodamalis cuestae sit on the table behind Rachel.

Sorry for the hiatus - graduation, etc.

...I've only been trying to graduate in the meantime. I'll admit, last October it wasn't looking great: I had a month and a half left of the fall semester, and one more semester after that in order to finish up all my courses, take my comprehensive exams, write my thesis, and defend it. I had already been in graduate school for slightly over two years, and now my third year was nearly halfway gone: I had a goal of submitting a draft of my thesis before the end of the semester, and at the time it didn't seem terribly realistic. I must have broken some world records though: I had my 110 page thesis written in three weeks flat (the week before thanksgiving, and then the two weeks afterward before winter break). What's strange is that it wasn't a total piece of crap either: it only required minimal editing by my advisor (and eventually my other committee members).

Apparently MSU prefers students to NOT take comps and do their defense in the same semester: I spent most of the early spring semester editing my thesis and constructing figures, and didn't get around to my comps until April 1; I did my defense only three weeks later. I am in no way trying to brag: it was hell, and if the same fate befalls you, well, you screwed up. Don't let it happen. That being said, however painful it is - it IS possible to do it all in such a short span of time if you stick to it, motivate yourself, and keep distractions (i.e. PC games, hiking, artwork) to a minimum.

My defense was on April 25 if I recall correctly: I didn't have much in the way of terribly difficult questions (I feared for the worst if certain parties arrived), and my committee really didn't have too many edits for me: many of them were time consuming because I had to look up some new articles. I spent most of finals week going over final edits, and formatting. I spent most of the two weeks after finals still working on formatting. We'll see if my thesis ever gets accepted by DGE.

Then around May 20 I drove out to California: I drove out through oregon to visit a couple fossil sites, and didn't find crap; I was home for about a day until I drove up to Lake Tahoe for the weekend, and then I had to leave there a day early to go and meet Dick Hilton up at Point Reyes, CA for fieldwork (some posts on that later). We found some great, exciting stuff...

I was home for two days after Pt. Reyes until I had to drive ALL the way down to San Diego for the Sixth Triennial conference on the Secondary Adaptation of Tetrapods to Life in the Water (SATLW). In fact, while on the beach in Bolinas in Marin County, I got a voicemail from Tom Demere (curator of the San Diego Museum and co-host of the conference) saying that my talk had been moved up to monday afternoon. I was pretty freaked out, because I had not yet shortened my talk from my 50 minute thesis presentation down to 18 minutes for the conference presentation, and I had two days to work on it.

Anyway, more about the conference soon. I think you can tell that I haven't had adequate time since my defense to do any blogging - but have no fear! The metal bars of my thesis and graduate school have (temporarily) disappeared and I can once again do 'fun stuff'.

Research featured on MSU homepage

Hey Folks,

Earlier in the week, MSU news service published an article featuring my research on fossil marine mammals.

You can view the article here: http://www.montana.edu/cpa/news/nwview.php?article=9818&origin=homepage-l

Thesis defense: Passed

Hey Folks,
Sorry for the unannounced month-long delay; I have had zero time to contribute to the blog because I've been busy trying to finish my master's thesis, which I successfully defended a week ago today. I've been consumed with edits and other last minute work over the last week, and still have a bit of thesis writing left for this iteration.
I'm nearing the end of the master's degree journey and all that crap; my folks are flying up here for my graduation on Friday.

Once I have my next draft in, I'll be writing up an actualistic taphonomy article on "What's currently happening to Osama Bin Laden's corpse?" In addition to its humorous objectives, it really will be an exercise in deep-sea taphonomy.

Deadline for Aquatic Tetrapods meeting has been extended

For all you other marine (and aquatic) tetrapod paleontologists (and biologists and anatomists) out there, the deadline for abstract submission for the 6th Triennial Conference on Secondary Adaptation of Tetrapods to Life in Water has been extended to May 1st.

That means that any of you who were hesitant about submitting something because you didn't have time because your master's level comprehensive exams were scheduled for the same day as the abstract deadline (and you totally kicked comps in the ass like a boss, and got your abstract on marine vertebrate taphonomy submitted anyway) can go ahead and take a couple more weeks to think about what you're going to submit.

Seriously, it should be a totally awesome meeting; aside from having events at a totally awesome institution like the San Diego Natural History museum and being organized by a couple of really great paleontologists (Annalisa Berta, Tom Demere, and their postdoc Eric Ekdale), it's in San Diego.

San Diego. In June. San Diego in June.

It's like going to Mexico for spring break, except there's marine mammal fossils, other paleontologists, the San Diego Zoo, and you don't have to worry about getting beheaded by drug cartel members and someone finding your head in a cooler on the side of the road (although if you decide to take a side-trip to Tijuana that could be a possibility).

I strongly urge all marine tetrapod folks to seriously think about submitting something; there are still plenty of slots open for oral and poster presentations, and the email that Eric sent out indicates that you can submit abstracts for an oral and poster presentation.

If you have projects concerning any of the following, SUBMIT SOMETHING!

-Cetaceans & other aquatic cetartiodactyls
-Pinnipeds
-Sirenians
-Desmostylians
-Other semiaquatic basal tethytheres
-Otters
-Polar bears
-semiaquatic rodents
-aquatic sloths
-Functional morphology of any of these critters
-Plesiosaurs & 'Pliosaurs'
-Placodonts
-Other whacky sauropterygians
-Thalattosaurs
-Mosasauroids and other 'pythonomorphs'
-Ichthyosaurs
-marine crocodylians
-TURTLES
-Marine iguanas
-Hesperornithiformes
-Penguins!
-Plotopterids
-Auks and Puffins! (Alcidae)
-Flightless cormorants (and other diving birds)
-all sorts of nonmarine aquatic birds I've forgotten
-Tanystropheus!

Again, here's the conference website:

http://www.sdnhm.org/satlw/